This invention relates generally to the transmission and detection of digital data using analog signals, and more particularly the invention relates to the detection of phase shift keying (PSK) encoded digital data.
The phase of a carrier signal can be used to encode digital data for transmission. The number of bits represented by a carrier phase symbol depends on the number of phases M of the carrier in an MPSK data burst.
A prior art approach to the detection of data symbols consists of using a phase locked loop to lock to the reference symbols and then detecting the data symbols using the phase reference out of the loop. A related approach is to use both reference symbols and remodulated data symbols to obtain a loop phase reference. These approaches are well known.
Another approach is to form a phase reference using a filtering operation on the reference symbols, often called pilot symbol aided demodulation. This approach is essentially the same as the phase locked loop approach in the sense that the phase locked loop also performs a filtering operation.
The present invention is concerned with maximum likelihood detection of data symbols in an MPSK data burst.